Based on the same rules as the hit KenKen(tm) game, as printed in the New York Times and The Times (uk).
Related to Sudoko, but with a mathematical twist - use the arithmetic challenges in each cage to help solve the puzzle.
Source code available under the GPL.
Authored by Ben Buxton, Paul Dingemans. Contributions by Pimm Hogeling, Stephen Lee, Alexander Tesfamichael, Anthony Paul.